I asked a friend, who runs his own BMW motorcycle shop in Charlottesville, VA and is one of the most knowledgeable technical minds on the marque in the country, to take a look at this thread. He's not much of a social media guy, but he told me to post as much of his thoughts as I wanted to. So here's his email in total:

Originally Posted by Virginia Motorrad

1) Run all of the lubricated components right way up, so their oil channels work as designed. Otherwise you are likely to oil starve something.

2) Run the Paralever right way up. Itís already been engineered to support loads that way, and the spiral gears are designed to thrust in one direction (they are cut differently for LHD and RHD). I donít think there would be a problem running with the link in tension, as on the R11xx models, but thereís just no need to go there especially since the R1200 Paralever seems better suited to the powertrain adaptation.

3) Peraves went down this road when they made the E-tracer (aka Zerotracer) out of the existing Monotracer design, which uses a K12RS engine with K100 trans/swingarm/FD. The E-tracer used a gutted 1-speed gearbox as a convenient way to interface the AC Propulsion motor to the driveshaft. For an electric street bike, I would look at the motor RPM and torque, and decide what top end you really want and see what one gear ratio will do. Given that the K1200S with a gas engine can basically do everything in one gear (second), Iíd think that the electric one definitely could. Itís not worth building a two or three speed gearbox. Itís probably simpler to just start with a stock R1200 gearbox and manually select gears at a standstill. I suspect the rider would very quickly settle on one gear and then you can build a 1-speed version accordingly. Iíd be happy to do that part.

The inherent problem with the gearbox idea, really with the BMW layout in general, is that the drivetrain becomes long. Peraves fought this. Giving up 8~10Ē of space just for gear reduction is very inefficient. However, the K12 is probably a good chassis for this since it is pretty long anyway. Iím thinking, would it would be better to use the whole K12S driveline with the electric motor running transverse? But support and oil sealing for the gearbox become harder, you are modifying shafts and cutting away engine cases and so forth; I would pursue the R1200 gearbox concept first.

Wow, that's very cool. Thank you for asking and many thanks to your friend for weighing in. His thoughts confirm my misgivings about inverting the transmission. He is also spot on on the length issue. Transverse mounting gets used for a reason. That begin said, the length of the k12 frame and the orientation of the shaft drive works in my favor with a longitudinal mounting. If the R1100RS transmission doesn't seem to mount well, attempt three might be an r1200 swing arm paired with the transmission I already have (but right side up). The advantage of the R11RS setup is that I think I will be able to mount it a little further back and gain some of that length back.

R1100rs transmission arrived - Thanks, CF! It looks like it handily solves my length issues, but might make everything sit higher in the frame. Its going to take some frame grinding to fit it in before I can see for sure. Picked up an RS swingarm and paralever for $10 (!) from a local yard. Now I need to see if one of my shafts will fit.

R1100rs transmission arrived - Thanks, CF! It looks like it handily solves my length issues, but might make everything sit higher in the frame. Its going to take some frame grinding to fit it in before I can see for sure. Picked up an RS swingarm and paralever for $10 (!) from a local yard. Now I need to see if one of my shafts will fit.